Stomach-action molluscicides

ABSTRACT

A stomach-action molluscicide, which includes a metal complexone and a suitable additive for enhancing the molluscicidal activity of the metal complexone. The additive may be selected from a surfactant or an additional source of ferric ions. Examples of the surfactant include sodium dodecyl sulphate or sorbitan monostearate, while an example of the additional source of ferric ions is ferric orthophosphate.

This application is a national stage application filed under 35 U.S.C. §371 of PCT Application No. PCT/AU98/00941, filed Nov. 12, 1998.

FIELD OF THE INVENTION

The present invention relates to improved stomach-action molluscicides.stomach poisons or edible baits containing them and their use inkilling, controlling and/or inactivating molluscs, in particular, slugsand snails. More particularly, the present invention relates to astomach-action molluscicide containing at least one additive, which isspecifically included to increase the efficacy of such a molluscicideand which lowers the cost of production of such a molluscicide.

BACKGROUND TO THE INVENTION

Slugs and snails are major pests of agriculture in many parts of theworld. The ecologies of different types of molluscs, which can be eitherterrestrial or aquatic, are very different and they usually requiredifferent types of treatment. The snail species, Cepaea hortensis, Thebapisana, Helix aspersa, Cernuella virgata and Achatina spp and the slugspecies, Deroceras reliculatum, Arion hortensis, Milar budapestensis andLimax maximus are of particular interest as targets. The common gardensnail, Helix aspersa and the grey field slug, Deroceras reticulatum, arecommon garden pests throughout Australia. On the other hand, there aregroups of snails, which have been introduced into Australia in thetwentieth century that are ever increasing in number. These are thewhite Italian snail, Theba pisana, and the vineyard or Mediterraneansnail, Cernuella virgata, which both cause extensive crop damage.

Significant crop damage by molluscs also occurs in northern Europe, theMiddle East, North and Central America, South East Asia, Japan and NewZealand. In many cases, the rise to pest status of the slug or snail inquestion is a consequence of change—either in distribution (as in thecase of accidental or deliberate introductions) or in agriculturalpractice, where crops or systems of cultivation may enable populationsto rise to pest levels. Slugs are a major agricultural pest which causesignificant crop damage by burying themselves in the soil and thenmoving along into holes drilled for planting new crop seeds in. Once theseed has been placed in the drill holes, they eat the inside out of thenew seed, thereby potentially destroying the whole planting.

Chemical methods (i.e. the use of molluscicides), involving the use ofstomach poisons for the control of such pests, are well known.Molluscicides containing metaldehyde and methiocarb have been in use forsome while. The use of metal complexes in stomach-action molluscicideswas first proposed by Henderson et al. in “Aluminium(II) and Iron(III)complexes exhibiting molluscicidal activity,” Australian PatentAU-B-22526/88. In one of their studies, these workers compared therelative toxicities of some aluminium and iron salts and chelates andtheir efficacies as stomach poisons, by injecting known amounts into thegut lumen of molluscs and they found that, in fact, the metal chelateswere more toxic than their corresponding salts. Metal chelates were alsofirst trialed by Henderson et al as contact-action poisons. In oneparticular study, Henderson used the metal chelate, FeEDTA, as the toxicagent, finding it just as effective as various salts of Fe(III).(Henderson, I. F. et al, in “A New Group of Molluscicidal Compounds,”BCPC mono., (1989), 41, “Slugs and Snails in World Agriculture”, pp289-294 eds. Henderson, I. F., British Protection Council, Farnham, U.K.).

More recently, Puritch el al in “Ingestible Mollusc Poisons,”International Patent Application No. WO 96/05728 claimed a terrestrialmollusc stomach poison containing, as the active ingredient, eitherferric edetate or the ferric hydroxy-ethyl derivative of edetic acid.These workers have also shown that mixtures of iron salts such as ferricsulphate, ferric chloride or ferric nitrate when mixed together withdisodium EDTA or EDTA, as such, are toxic to the slug species, Derocerasreliculatum.

The term “stomach-action molluscicide” is used herein in its broadestsense and includes a molluscicide, which is capable of being ingestedinto the stomach of the mollusc in an effective amount so as to killand/or inactivate the mollusc.

The term “metal complexone” is used in its broadest sense and refers toa chelate of a metal with at least one ligand of the complexone type.The term “complexone” as used herein refers to an organic ligandcontaining at least one iminodiacetic group —N(CH₂CO₂H)₂, or twoaminoacetic groups —NHCH₂CO₂H₂, or a derivative of either of these wherethe —CH₂ group is substituted, which form complexes with most cations.Suitable complexones include those disclosed in Wilkinson, G.,“Comprehensive Coordination Chemistry,” Volume 2, Chapter 20.3, pp777-792 which is incorporated herein by reference.

In general, most toxic compounds are also repellent and the interactionof toxicity with repellency prevents the ingestion of sufficient poisonto kill the mollusc. Therefore, the essential problem that an effectivestomach-action molluscicide has to overcome is that of palatabilitysince in order for it to be effective, it must be ingested by themollusc. Although Puritch et al claimed that their formulations providea palatable molluscicide, indeed tests carried out on these formulationsby the present inventor revealed the acidic, and hence possiblyunpalatable, nature of these formulations. It is believed that asignificant proportion of the efficacy, claimed by Puritch et al, ispossibly due to the molluscicidal formulation of either ferric edetateor the ferric hydroxy-ethyl derivative of edetic acid, or indeed,mixtures of iron salts, such as ferric sulphate, ferric chloride orferric nitrate, when mixed together with disodium EDTA or EDTA, actingas a contact poison rather than an ingestible poison. It is furtherbelieved that the claimed palatable nature of these formulations arisesnot so much from the inclusion of the specific active ingredient, butrather from the elements of the “inert” carrier containing bran/flourand a phagostimulant, which would cause the bait to be sufficientlypalatable to allow ingestion.

The present inventor therefore initially sought to develop amolluscicide, wherein the active ingredient itself was more palatable,efficacious and also one which was not harmful to the environment. Inthis, the present inventor was successful and developed and made anapplication for a patent, International Patent Application No:PCT/AU97/00033, for a stomach-action molluscicide, containing thehydroxy compound, [Fe(OH)EDTA]²⁻ or its dimer, [EDTA-Fe—O—Fe-EDTA]⁴⁻ asthe active ingredient, which was found to be more palatable to molluscsand therefore also more efficacious.

The present inventor serendipitously discovered that the addition ofK₂CO₃ or CaCO₃ as a filler to a molluscicidal bait containing FeEDTA,resulted in a bait that was more effective than with no additionalfiller being added. These fillers also fortuitously acted as pHadjusters which effectively adjusted the pH of the bait to around 8. Atlow pH, the Fe(III) atom in FeEDTA is surrounded by the two nitrogenatoms and the four oxygen atoms, provided by the hexadentate ligand,EDTA, and a water molecule acting as an additional seventh donor ligand.At a pH above 7, the water molecule is replaced by either an —OH groupor an —O— group. At a pH of between 7 and 10, the species present in themajority are [Fe(III)(OH)EDTA]²⁻ or its dimer, [EDTA-Fe—O—Fe-EDTA]⁴⁻with Fe(III)EDTA being present in the minority. The hydroxy compound andits dimer are in equilibrium, the relative amounts depending on themoisture of the pellet. According to F. G. Kari et al, Environ. Sci.Technol., (1995), 29, 1008, at a pH of about 8 to 8.5, there isvirtually no Fe(III)EDTA present at all. The present inventor has foundthat molluscicides having a pH of greater than 7, but less than 9 or 10appear to be more palatable than those having a pH of 7 or below. Inaddition, at higher pH, the Fe(III) ions are more readily replaced bvCa²⁻ions, liberating the Fe(III) ions for passage through the intestinalepithelium into the blood stream. It is suggested that these Fe(III)ions may then complex with haemocyanin present as the oxygen-carrier inthe blood of the mollusc, in some as yet unexplained way, resulting inan inhibition of the oxygen uptake by the mollusc, leading to itseventual death.

A further essential requirement for an efficacious stomach-actionmolluscicide is that premature termination of feeding must not result sothat an insufficient amount of poison is ingested to kill the pest. Inthis way, the molluscicide needs to be more than a feeding deterrent ora crop protectant. One way of achieving this is to increase theconcentration of active ingredient present in the bait. However, thisleads to excessive costs of production and to a bait that is moreharmful to non-target animals. This latter consideration is ofparticular concern since stomach-action poisons are often consumed bynon-target organisms such as domestic animals, birds and children,particularly when baits are used. There is always a possibility that thebait will be consumed by such non-target organisms. Accordingly, thepresent invention seeks to improve the efficacy of the bait in such away as to further decrease its harmful effects on non-target organisms.

Surprisingly, the present inventor has now found that the addition ofsurfactant to the molluscicidal formulation disclosed in InternationalPatent No. PCT/AU97/00033 provides significant advantages over thatformulation. Surfactants are principally known as agents, which reducethe surface tension of liquids and have been particularly widely used inthe detergent industry. Surfactants have also been used in themolluscicidal industry, but principally for their emulsifyingcharacteristics (Albright & Wilson, Patent No. GB 2 252 499 A, (1992))and to facilitate the milling process of the molluscicide (Tavener etal, Patent No. AU91178623). Henderson et al have shown that the efficacyof stomach-action molluscicides, containing metaldehyde and methiocarb,both highly toxic active ingredients, can be increased by the additionof small amounts of additives (Henderson et al, Ann. appl. Biol.,(1992), 121, 423-430); (Bowen et al, Patent No. GB 2098 869 A, (1982)and Bowen et al, in BCPC Symposium Proceedings, (1996), 66, “Slug &Snail Pests in Agriculture,” pp397-404).

A number of surfactants in the form of their aqueous solutions wereclaimed to have molluscicidal activity on aquatic snails. (Visser, S.A., Bull. Wld. Hlth. Org., (1965), 32, 713-719). Visser found thataqueous solutions of cationic detergents were on the whole more toxicthan the anionic or non-ionic detergents used as aqueous solutions.Dawson et al, in BCPC Symposium Proceedings, (1996), 66, “Slug & SnailPests in Agriculture,” pp 439-444, eds. Henderson, I. F., BritishProtection Council, Farnham, U. K.) have investigated the repellency ofa range of surfactants to the slug, Deroceras reticulatum. They foundthat in particular, tetraammonium salts were highly repellent and somepolyphenylpolyethoxylates were also repellent with the degree ofrepellency varying with the degree of ethoxylation. These workers wereinterested in using surfactants as a repellent to crops. Theirlaboratory tests showed that crawling slugs rapidly detect and aredeterred by topical applications of chemicals at low deposit rates. Theyconcluded that surfactants were of limited use in this type ofapplication, since they were rapidly removed from the plant by rain andby condensation.

Selected surfactants are considerably less toxic to mammals than others.Sodium dodecyl sulphate (SDS) is a surfactant, which is widely used asan emulsifier in agricultural chemicals. It is a popular choice amongstsurfactants, since it is biodegradable and is generally regarded asbeing environmentally safe. Tseng et al, in Proceedings of the NationalScience Council, R. O. C., Part B: Life Sciences, Vol. 18, No. 3,(1994), pp 138-145, found that sodium dodecyl sulphate (SDS) was aneffective molluscicide, when used on its own at a concentration of 100ppm, for the semi-aquatic golden apple snail, Pomacea canaliculata. SDSwas used in this case as an aqueous solution applied onto the watersurface. Tseng et al also observed that snail movement and vitalresponse stopped sooner at an acidic pH compared with at an alkaline pH.These workers believed that the molluscicidal activity of SDS appearedto be due to “dermal” absorption, rather than as an “oral” (stomach)poison.

However, although the use of surfactants have been studied in the past,the synergistic effects of surfactants with metal complexones inmolluscicidal formulations or compositions have not been previouslystudied.

The present inventor found that several surfactants, tested under theexperimental conditions leading to the present invention, exhibited noefficacy when used on their own on terrestrial molluscs. Accordingly,experiments were designed wherein the surfactant was employed incombination with a known stomach poison and it was found that asynergism exists between the metal complexone and the surfactant. Theinclusion of surfactants as the synergistic additive in stomach-actionpoisons, in accordance with the present invention, offers considerableadvantages over the presently known stomach-action molluscicides. Sinceit was believed that the surfactant would exhibit a synergistic effectwith the metal chelate, its inclusion in the composition might enablethe amount of metal chelate utilised in the composition of the bait tobe reduced. Not only would this further reduce the harmful effects ofthe molluscicide on non-target organisms, but also, since less metalchelate would be required to produce the same level of efficacy, theinclusion of the surfactant might significantly lower the cost ofproduction.

It is well known that the inclusion of the poison in a bait, as apellet, gives significantly better results than the direct applicationof molluscicide lo the soil or application of the bait as a powder tothe soil. Details of bait formulation in the prior art have generallybeen given without discussion of differences that might be expected fromother formulations. Such differences are most probably significant indetermining the amount of chelate required for effective control.Indeed, it is now believed by the present inventor that some of theferric ions of the active ingredient, [EDTA-Fe—O—Fe-EDTA]⁴⁻ actuallyreact with the phytates or other natural chelating agents present inbran, a major component of the bait composition, making them unavailablefor toxic action. Investigations were consequently carried out as to theeffect of the addition of an additional source of Fe(III) ions to thecomposition of the bait, with the belief that such addition wouldfurther increase the efficacy of the bait. A further consideration tothis aspect of the present invention is the quality of the bran used inthe composition. Fine, low-quality bran is relatively inexpensive, butuse of this type of bran leads to a low rain-resistant pellet. On theother hand, extremely fine bran, known as “pasta bran,” coupled withappropriate water-resistant additives can lead to a highlyrain-resistant pellet. This latter alternative can be expensive and can,in fact, be more expensive than the total cost of all the otheringredients of the formulation. Since the amount of bran used in theformulation as a proportion of the total weight of the bait isconsiderable, the higher the percentage of bran, the higher the cost ofproduction of the bait. It was believed that by increasing the amount ofsurfactant added, due to the synergistic effect, the amount of FeEDTArequired might be lowered. As discussed above, since a percentage ofadded FeEDTA is removed from being available for molluscicidal activityby complexing with phytates or other natural chelators present in thebran, by lowering the amount of bran used, a higher percentage of FeEDTAis available for toxic action. Additionally, the cost of productionwould be lowered since the amount of bran is reduced. However, it wasbelieved that a reduction in the amount of bran used might lower theattractiveness of the bait to the molluscs, since the bran is a majorcomponent affecting the palatability of the bait and therefore a balancebetween all these competing factors was required to be established.

Additional studies were therefore aimed at further lowering the amountof FeEDTA required for an effective kill rate and hence providing amolluscicide that was more cost effective to produce. Thus, experimentaltrials were designed where FeEDTA, in combination with an additionalsource of iron, were incorporated into the bait formulation.

Accordingly, it is an object of the present invention to combine therequirements of palatability of the molluscicide so that the poison isreadily ingested, with the requirements of an effective amount ofavailable Fe(III) ions, together with at least one additive that willincrease the rate of absorption of the poison. It is also an object ofthe present invention to incorporate an additive, which complements andenhances the existing environmentally-friendly aspects of the use of theactive ingredient, [Fe(III)(OH)EDTA]²⁻ or in the form of its dimer,[EDTA-Fe—O—Fe-EDTA]⁴⁻. In addition, the present invention provides apalatable, efficacious molluscicide, which is also less expensive toproduce.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided astomach-action molluscicide including an effective amount of a metalcomplexone, an effective amount of at least one additive, excluding ametal carbonate, for enhancing the molluscicidal activity of the metalcomplexone, and a suitable non-liquid carrier therefor, wherein themetal of the metal complexone is selected from the group consisting ofGroup 2 metals, transition metals or Group 13 metals.

Preferably, the metal of the metal complexone is a transition metal.More preferably, the metal is selected from the group of iron(II) oriron(III), aluminium or copper. Most preferably, the metal is iron(III)or copper(II). Preferably, the complexone is ethylenediaminetetra-aceticacid or hydroxyethylethylenediaminetriacetic acid.

Preferably, the metal complexone is selected from the hydroxy-metalcomplexone, [Fe(III)(OH)EDTA]²⁻, its dimer [EDTA-Fe—O—Fe-EDTA]⁴⁻, orFeHEEDTA.

In a preferred form of the invention, the additive is a surfactant,wherein the surfactant is selected from the group of cationic, anionicor non-ionic surfactants. More preferably, the surfactant is anionic ornon-ionic. Most preferably, the anionic surfactant is selected from thegroup comprising sodium dodecyl sulphate (SDS), calcium benzyl dodecylsulphate (ALKANATE CS®) or ammonium dodecyl sulphate (ADS), but is in noway limited to these. Even more preferably, the surfactant is sodiumdodecyl sulphate (SDS). When the surfactant is non-ionic, it is mostpreferably selected from the group of SPAN-type surfactants, comprisingsorbitan monostearate and sorbitan monooleate.

Typically, the amount of surfactant required for efficacy is betweenabout 0.05-1% of the weight of the molluscicide. Preferably, the amountis between about 0.1-0.4% by weight of the molluscicide. Mostpreferably, the amount is about 0.2% by weight of the molluscicide.

Typically, when used in combination with a surfactant, the amount ofmetal complexone required for efficacy is between about 3-7% by weightof the molluscicide. Preferably, the amount is between about 3-5% byweight of the molluscicide. Most preferably, the amount is about 3.5% byweight of the molluscicide.

In a preferred form of the invention, the non-liquid carrier for themetal complexone usually includes a mollusc food, such as a cereal,wheat flour, bran, arrowroot or rice flour, carrot, beer, rice hulls,comminuted cuttle fish, starch or gelatin, so that the mollusc isattracted to the edible bait. Non-nutrient carriers of interest includenon-nutrient polymeric materials, pumice, carbon and materials useful ascarriers for insecticides. The poison or bait may also contain otheradditives known in the art, such as mollusc phagostimulants, forexample, sucrose or molasses; lubricants, such as calcium or magnesiumstearate, talc or silica; binders which are suitably waterproof, such asparaffin wax, white oil or casein and flavouring agents such as BITREX®(a registered trade mark), which imparts a bitter taste and renders thepoison or bait less attractive to non-target organisms and children. Inorder to inhibit deterioration of the poison or bait, preservatives suchas sodium benzoate, vitamin E, alpha-tocopherol, 4-nitrophenol, ascorbicacid, methyl paraben, propyl paraben or sodium bisulfite may also beincluded.

Preferably, the waterproofing agent is selected from Guar gum, Lotusbean gum or a fatty acid alcohol. Typically, where the waterproofingagent is a fatty acid alcohol, this is present in an amount aboutbetween 1-5% by weight of the molluscicide. More preferably, the fattyacid alcohol is selected from the group of C₁₆-C₁₈ fatty acid alcohols.Most preferably, the C₁₆-C₁₈ fatty acid alcohols comprise about 2% byweight of the molluscicide and the C₁₆-C₁₈ fatty acid alcohol isHYDRENOL MY, which is a mixture of hexadecanol, heptadecanol andoctadecanol.

To increase the density of the actual mixture before pelletising toreduce the airborne content and thus wastage of the mixture, a filler isadded to the carrier. Preferably, the filler contains calcium ormagnesium ions to assist in the replacement of iron in the metalcomplexone of the active ingredient. Typically, the filler is selectedfrom CaCO₃K₂CO₃, MgCO₃, or a combination of these, or CaSO₄, but is notlimited to these. More preferably, the filler is a metal carbonate,which is present in a sufficient amount so that the pH is non-acidic.Typically, the poison or bait contains about 1-5 wt % of a metalcarbonate as a filler. When the metal carbonate is CaCO₃, the preferredconcentration is about 2-3% by weight of the molluscicide. When themetal carbonate is K₂CO₃, the preferred concentration is about 4-5% byweight of the molluscicide. When the metal carbonate is MgCO₃, thepreferred concentration is about 0.5-5% by weight of the molluscicide.

Serendipitously, such a metal carbonate additionally acts as a pHadjustment agent and it was found that the efficacy of the molluscicidegenerally increased with an increase in pH up to a pH of about 10. At apH of about 10, it was found that feeding was deterred. It was found,through trials which were carried out using various amounts of CaCO₃,MgCO₃ and K₂CO₃ combined, that a balance needs to be struck between thepH and the attractiveness of the bait to the molluscs. If the pH of thebait is too low, it has been found that the efficacy is significantlyreduced. Preferably, the pH of the molluscicide is non-acidic.Typically, the molluscicide has a pH of about 7 and not exceeding 10.Preferably, the pH of the molluscicide is about 8. Preferably, the pHadjustment agent is CaCO₃ or MgCO₃. The amount of metal carbonate addedlargely depends on the other constituents present in the formulation. Ingeneral, a stomach poison having a neutral or alkaline pH, has proved tobe more efficacious than one having an acidic pH. The K₂CO₃, CaCO₃ orMgCO₃ used as a filler and which adjusts the pH to about above 8, aidsin the formation of the metal complexone, [Fe(OH)EDTA]²⁻ or its dimer,[EDTA-Fe—O—Fe-EDTA]⁴⁻. The relative amounts of each of the two differentforms of the active ingredient will be determined by the amount ofmoisture present in the pellet.

According to another aspect of the invention, when the metal complexoneis the hydroxy-metal complexone, [Fe(III)(OH)EDTA]²⁻ or in the form ofits dimer, [EDTA-Fe—O—Fe-EDTA]⁴⁻, the molluscicide further includesadditional Fe(III) ions added to the bait composition to ensure that aneffective concentration of Fe(III) ions is present in the bait. Suchaddition of Fe(III) ions is to counteract the binding of Fe(III) withthe phytates present in the bran or flour present in the carrier,thereby allowing maximum efficacy of the poison. Preferably, theadditional Fe(III) ions are added in the form of a ferric salt or in theform of a clay to the composition of the bait. Typically, the clayemployed is both one which contains a high concentration of Fe(III) andin the form which is suitable for use in the pelletiser. Preferably, theclay is a form of terracotta clay. More preferably, the clay is in theform of a powder.

Preferably, when the additional Fe(III) ions are added in the form of aferric salt, the ferric salt is ferric orthophosphate. Typically, theamount of ferric orthophosphate required for efficacy is between about1-5% by weight of the molluscicide. Preferably, the amount required isbetween about 1-3% by weight of the molluscicide.

Typically, when in combination with an effective amount of an additionalsource of iron and an effective amount of metal carbonate, the amount ofmetal complexone required for efficacy is between about 1-9% by weightof the molluscicide. Preferably, the amount is between about 2-3% byweight of the molluscicide. Most preferably, the amount is about 2.5% byweight of the molluscicide.

In a preferred embodiment, the additive is a surfactant in combinationwith an additional source of ferric ions. More preferably, themolluscicide includes a metal complexone, a surfactant, an additionalsource of ferric ions and a metal carbonate. Most preferably, themolluscicide includes an effective amount of FeEDTA, an effective amountof sodium dodecyl sulphate (SDS), an effective amount of ferricorthophosphate and an effective amount of calcium carbonate. Mostpreferably, the amount of FeEDTA is 2-3% of the weight of themolluscicide, the amount of SDS is about between 0.1-0.2% of the weightof the molluscicide, the amount of ferric orthophosphate is betweenabout 1-2% of the weight of the molluscicide and the amount of calciumcarbonate is between about 3-4% of the weight of the molluscicide.

The molluscicide is advantageously presented in a solid form such astablets, a powder, granules or pellets. Those skilled in the art willappreciate that it is preferable to prepare the products, which are thesubject of the invention, in a form that is easy for consumers to use.Pellets, for example, can be easily scattered from a box across the areato be protected. Preferably, the molluscicide is in the form of apellet. More preferably, the pellet is between 1 and 4 mm long and lessthan 3 mm in diameter. Most preferably, the pellet is 1.5 mm long and1.5-2.0 mm in diameter.

It is to be understood by those skilled in the art that the scope of thepresent invention includes the stomach-action molluscicide disclosedherein, when used in combination with at least one other molluscicide.

According to another aspect of the invention, the method of preparationof the stomach-action molluscicide in pellet form includes the steps of:

(i) blending the components together to form a blended composition;

(ii) heating the blended composition for about 1 to 5 minutes inthe-presence of steam at an ambient temperature of between about 80° and100° C.;

(iii) maintaining the composition at the ambient temperature betweenabout 10 and 30 seconds; and

(iv) forming the blended composition into one or more pellets.

Preferably, step (ii) is carried out at about 90° C. for about 2minutes, whereafter step (iii) is carried out for about 15 seconds.Preferably, the blended composition is formed into pellets underpressure. Throughout this specification and the claims which follow,unless the context requires otherwise, the word “comprise,” orvariations such as “comprises” or “comprising,” will be understood toimply the inclusion of a stated integer or group of integers but not tothe exclusion of any other integer or group of integers.

EXAMPLES

The invention will now be illustrated with reference to the followingnon-limiting Examples:

There are many possible variables to consider when evaluating snail orslug pellets. Field trials are often poorly controlled and it is oftendifficult to arrive at unambiguous conclusions. It is possible to applyextensive statistical analysis to poorly designed or controlledexperiments. However, a series of simple experiments in which variablesare controlled lead to unambiguous conclusions with no need forstatistical analysis. It was decided to compare the pellets underlaboratory conditions which could closely mimic controlled fieldconditions, but would not present problems arising from incompletecollection and counting of dead specimens or non-uniform distribution ofsnails in the trial patches. No attempt was made to control the diurnaltemperature or the length of daylight, even though it was known thatthese factors do play some part in snail and slug feeding activity buttheir role is minor compared with the effect of temperature.

In designing experiments to investigate the synergistic effects ofsurfactants with metal complexones in stomach-action poisons, it isnecessary to consider at least the following variables:

(i) the bait formulation from the perspective of palatability;

(ii) the amount of surfactant used;

(iii) the concentration of the metal complexone used;

(iv) the species of mollusc upon which the molluscicide is to beeffective; and

(v) the maximum daily temperature range over which the molluscicide mustbe effective.

The inventor had already concluded that there is a direct relationshipbetween temperature and feeding in the consideration of the efficacy ofmetal complexone-based molluscicides. (Young, C. L., in “Metal chelatesas stomach poison molluscicides for introduced pests, Helix aspersa,Theba pisana, Cernuella virgata and Deroceras reticulatum in Australia,”BCPC mono., (1996), 66, “Slug and Snail Pests in Agriculture,” eds.Henderson, I. F., British Protection Council, Farnham, U. K.). While theideal feeding temperature for snails is around 20° C., the temperatureshould be about above 10° C. because at temperatures below this, feedingis considerably reduced. For Helix aspersa, under high humidityconditions the ideal feeding temperature is approximately 20°-25° C.,whereas for Deroceras reticulatum, it appears to be considerably lowerand probably about 15° C. in high humidity conditions.

For convenience in this experimental work, the snail species used wereCochlicella barbara and Helix aspersa and the slug species, Derocerasreticulatum. In the trials conducted, all snails could be accounted for,whereas a few of the slugs apparently disappeared. It is possible thatthe slugs died and decomposed but cannibalism could not be ruled out.Indeed, cannibalism in slugs has been reviewed (South, A., “TerrestrialSlugs: Biology, Ecology and Control,” (1992), Ch. 11, Chapman & Hall,London) and the existence of cannibalism in slugs has been noted even inthe presence of food. (Airey, W. J., “Laboratory studies on damage topotato tubers by slugs,” in J. Mollusc. Stud., (1987), 53, 97-104).

Experiments were carried out in “plots,” each “plot” consisting of acontainer of volume approximately 500 cm³ and a total internal surfacearea of 300 cm¹. About ten small airholes, of 0.2 mm diameter, were madein the lid of each container. Fresh carrot slices or cabbage were usedas an alternative food.

The metal complexone and the additive of the stomach poison are normallyincorporated in a carrier, all three elements together constituting themolluscicidal bait. The non-liquid carrier of the present invention isbased on wheat flour/bran and is typical of common carriers used inbaits used throughout the world. Although the basic constituents ofwheat flour/bran-based baits, as described by the present inventor inInternational Patent Application No. PCT/AU97/00023, are well-known inthe industry, further experimentation for the purposes of the presentinvention was carried out.

Contrary to what appears to be commonly shared belief in themolluscicidal industry, the present inventor believes that the carrieris thought not to be inert, but rather that it binds the metal ionsmaking them less available for effective molluscicidal activity. Thereactive nature of phytates. which are natural chelating substancespresent in bran and wheat flour, is well known and extensivelydocumented. A further aspect of the present invention therefore was toattempt to counteract the complexing of the Fe(III) ions with thephytates in the wheat flour and in the bran of the carrier.Consequently, investigations as to the lowest possible amount of bran inthe formulation were carried out so as to further reduce the cost ofproduction of the bait. The lower the amount of bran, the higher theconcentration of active ferric ions that is available for molluscicidalactivity i.e. the amount of metal complexone required to produce thesame level of molluscicidal activity is reduced and, together with alower amount of bran, these factors together lead to a lower cost ofproduction. The addition of a surfactant, for example, to theformulation, which displays a synergistic effect with the metalcomplexone, further reduces the amount of metal complexone required toproduce the same molluscicidal efficacy. Since the amount of surfactantneeded to replace roughly 3% of metal complexone to give a similarefficacy is only 0.2% and the cost of surfactant is roughly equivalentto the metal complexone, the addition of surfactant to replace some ofthe metal complexone in the composition results in an overall lower costof production.

Three different groups of trials were undertaken in order to clarify therelative influence of phytates in bran. These involved:

a) FeEDTA +sodium phytate;

b) FeEDTA +various proportions of bran; and

c) FeEDTA +various levels of iron from simple salts.

The surfactants used in the trials were specifically limited to be thosewhich reinforce the environmental benefits of FeEDTA and the hydroxyderivative of FeEDTA, [Fe(OH)EDTA]²⁻ or in the form of its dimer,[EDTA-Fe—O—Fe-EDTA]²⁻. The toxicity, LD₅₀ values of several commonsurfactants for rat by oral administration are tabulated below forillustration purposes:

Toxicity, LD₅₀ values of several common surfactants for rat by oraladministration. LD₅₀ Surfactant g/kg Sodium dodecyl sulphate, SDS 1.288Sorbitan monolaurate, (Span 20) 33.6 Sorbitan monostearate (Span 60) 31PEG* 300 27.5 PEG* 1500 44.2 PEG* 4000 50 PEG* 6000 60 PEG* 1000 oleylether 2.777 PEG* monostearate 44 *PEG is polyethylene glycol

In Example 1, the complexing effect of the phytates and other naturalchelators present in flour was investigated. The following formulationswere used:

Formulation A 2.50% FeEDTA + 0.868% dodecasodium phytate + FlourFormulation B 2.78% FeEDTA + 2.21% dodecasodium phytate + FlourFormulation C 2.67% FeEDTA + 0.587% ferric phosphate + Flour FormulationD 2.40% FeEDTA + 2.40% ferric phosphate + Flour

Example 1

In this Example, the variety of snail used was Helix aspersa and thetrial was carried out within a temperature range of 14-20° C. Six plotswere used in the trial. The dead snails were removed and counted after 8days. The results are shown in Table 1.

TABLE 1 Complexing effect of phytates and other natural chelatorspresent in flour. Formulation Kill Rate % Kill Rate Control 0/24  0%Formulation A 9/24 37% Formulation B 0/24  0% Formulation C 9/24 37%Formulation D 12/24  50%

Summary

Comparing the results obtained for Formulations A and B, since in theseformulations, the dodecasodium phytate simulates bran, it can readily beseen that with a lower amount of bran in the bait, the bait is moreeffective. Comparing the results obtained for Formulations C and D, themore additional ferric ions added, the more effective the bait, sincethe phytates and other natural chelating agents in the flour complexwith and therefore effectively remove some of the ferric ions from beingavailable for molluscicidal activity. The lower the amount of bran, thehigher the concentration of ferric ions available for molluscicidalactivity and therefore the greater the efficacy of the molluscicide.This experiment clearly shows that phytates in the flour and bran lockup ferric ions present in the bait and effectively limit theiravailability for efficacy.

In Examples 2 and 3, the efficacies of various surfactants incombination with FeEDTA and the hydroxy derivative [Fe(OH)EDTA]²⁻ weretrialed and compared to FeEDTA used on its own. The various surfactantstrialed were as follows:

Teric N40—an ethylene oxide derivative of nonyl phenol made by ICI

Sodium dodecyl sulphate

Ammonium dodecyl sulphate

ALKANATE CS®—Calcium benzyl dodecyl sulphate in butanol made by ICI

ATPLUS®-3001A—a polyethyleneglycol surfactant made by ICI

Teric 200—an alkylene oxide derivative of an alkyl phenol made by ICI

In Examples 2 and 3, the following formulations were used:

Formulation E 1.83% FeEDTA + 0.214% Teric N40 + Flour Formulation F2.60% FeEDTA + 0.556% Teric N40 + Flour Formulation G 3.53% FeEDTA +0.192% Teric N40 + Flour Formulation H 3.59% FeEDTA + 0.294% Teric N40 +Flour Formulation I 4.44% FeEDTA + 0.366% Teric N40 + Flour FormulationJ 0.75% FeEDTA + 0.152% SDS + Flour Formulation K 1.18% FeEDTA + 0.131%SDS + Flour Formulation L 1.93% FeEDTA + 0.147% SDS + Flour FormulationM 2.93% FeEDTA + 0.147% SDS + Flour Formulation N 3.00% FeEDTA + 0.182%SDS + Flour Formulation O 4.80% FeEDTA + 0.138% SDS + Flour FormulationP 5.50% FeEDTA + 0.197% SDS + Flour Formulation Q 0.95% FeEDTA + 0.157%ADS + Flour Formulation R 1.41% FeEDTA + 0.336% ADS + Flour FormulationS 1.49% FeEDTA + 0.273% ADS + Flour Formulation T 2.95% FeEDTA + 0.665%ALKANATE CS ® + Flour Formulation U 2.85% FeEDTA + 0.50% ATPLUS ® +Flour Formulation V 2.86% FeEDTA + 0.233% Teric 200 + Flour FormulationW 3.70% [EDTA-Fe—O—Fe-EDTA] + 0.12% SDS + Bran/Flour Formulation 1 0.42%FeEDTA + Flour Formulation 2 0.86% FeEDTA + Flour Formulation 3 1.52%FeEDTA + Flour Formulation 4 3.80% FeEDTA + Flour Formulation 5 4.70%FeEDTA + Flour Formulation 6 6.50% FeEDTA + Flour Formulation 7 7.70%FeEDTA + Flour

Example 2

In this Example, the variety of snail employed was Cochlicella barbara.The trial was conducted within a temperature range of 9-18° C. The deadsnails were removed and counted after 8 days. The results are shown inTable 2.

TABLE 2 Comparison of the efficacies of various formulations containingTeric N40 or SDS as surfactants in combination with FeEDTA. FormulationKill Rate % Kill Rate Control  0/30  0% Formulation E 20/30 67%Formulation F 19/30 63% Formulation G 24/30 80% Formulation H 24/30 80%Formulation I 20/30 67% Formulation J 19/30 63% Formulation K 19/30 63%Formulation L 25/30 83% Formulation M 27/30 90% Formulation N 26/30 87%Formulation O 20/30 93% Formulation P 27/30 90%

Example 3

In this Example, the variety of snail employed was Helix aspersa. Thetrial was conducted within a temperature range of 14-20° C. The deadsnails were removed and counted after 8 days. The results are shown inTable 3.

TABLE 3 Comparison of the efficacies of various formulations containingADS, ALKANATE CS ®, ATPLUS ®, Teric 200 or SDS as surfactants incombination with FeEDTA or the oxo-dimer, [EDTA-Fe—O—Fe-EDTA]⁺.Formulation Kill Rate % Kill Rate Control 0/24  0% Formulation Q 1/24 4% Formulation R 6/24 25% Formulation S 4/24 17% Formulation T 13/24 54% Formulation U 7/24 29% Formulation V 7/24 29% Formulation W 15/24 62% Formulation 1 0/24  0% Formulation 2 0/24  0% Formulation 3 0/24  0%Formulation 4 9/24 37% Formulation 5 12/24  50% Formulation 6 20/24  83%Formulation 7 15/24  62%

Summary

The results from Examples 2 and 3 show that a formulation containingsurfactant in combination with FeEDTA is generally more effective thanone containing FeEDTA on its own at a similar concentration. Forexample, a comparison of Formulations 3, 4 and 5 with Formulations E, F,G, L and N clearly show the enhancement of toxic action by the additionof surfactant to FeEDTA.

In Example 4, the efficacies of various surfactants in combination withFeEDTA were trialed and compared to FeEDTA when used on its own. Thefollowing surfactants were trialed although SDS would be less preferredthan the SPAN surfactants, sorbitan monostearate and sorbitanmonooleate, due to its increased toxic nature (Refer to the Table ofLD₅₀ values above):

SDS—sodium dodecyl sulphate

Sorbitan monostearate

Sorbitan monooleate

Cetyltrimethylarmmonium bromide

The various formulations used were as follows:

Formulation 8 3.4% FeEDTA + Flour Formulation 9 3.4% FeEDTA + 0.228%SDS + Flour Formulation 10 3.4% FeEDTA + 0.50% SDS + Flour Formulation11 2.2% FeEDTA + Flour Formulation 12 2.2% FeEDTA + 0.227% sorbitanmonostearate + Flour Formulation 13 2.2% FeEDTA + 0.279% sorbitanmonooleate + Flour Formulation 14 2.2% FeEDTA + 0.401% sorbitanmonooleate + Flour Formulation 15 2.2% FeEDTA + 0.76% sorbitanmonooleate + Flour Formulation 16 2.2% FeEDTA + 0.61%cetyltrimethylammonium bromide + Flour

Example 4

In this Example, the variety of snail employed was Helix aspersa. Thepellets used in the trial all contained FeEDTA with varying amounts ofsurfactant added. The trial was conducted within a temperature range of17-28° C. The dead snails were removed and counted after 8 days. Theresults are shown in Table 4.

TABLE 4 Comparison of the efficacies of various formulations containingdifferent amounts of surfactant in combination with FeEDTA. FormulationKill Rate % Kill Rate Control 0/24  0% Formulation 8 11/24  46%Formulation 9 18/24  75% Formulation 10 13/24  54% Formulation 11 5/2421% Formulation 12 15/24  63% Formulation 13 15/24  63% Formulation 148/24 33% Formulation 15 11/24  46% Formulation 16 3/24 12%

Summary

The results for Formulations 12 and 13 show that the efficacy ofsorbitan monosterate is virtually equivalent to that of sorbitanmonooleate. Also, the results from using Formulations 9 and Formulations13, 14 and 15 show that the efficacy is very dependent on the amount ofsurfactant added. The addition of too much surfactant could result in abait that is unpalatable. It can also be seen that the use ofcetyltrimethylammonium bromide, a cationic surfactant, in theformulation resulted in a reduction of the efficacy. This is believed tobe due to it being repulsive to molluscs and hence unpalatable.

In Example 5, the effect of the addition of varying amounts of clay tothe bait containing the active ingredient in the form of the oxo-dimer,[EDTA-Fe—O—Fe-EDTA]⁴⁻ was trialed and compared to the bait formulationcontaining no clay. This trial was both an investigation into thevariation of the efficacy of the pellet with the hardness of the pelletand to investigate whether the terracotta-type clay utilized whichcontains a higher proportion of Fe(III) ions than most other clays,could provide the additional Fe(III) required by bran-containing baits.

The various formulations used were as follows:

Formulation 17 5.07% [EDTA-Fe—O—Fe-EDTA] + Flour/bran Formulation 184.90% [EDTA-Fe—O—Fe-EDTA] + 3.3% Clay + Flour/bran Formulation 19 4.60%[EDTA-Fe—O—Fe-EDTA] + 8.7% Clay + Flour/bran Formulation 20 4.20%[EDTA-Fe—O—Fe-EDTA] + 17.7% Clay + Flour/bran Formulation 21 4.37%[EDTA-Fe—O—Fe-EDTA] + 13.8% bentonite* + Flour/bran *Bentonite is aclay-type material, which is used as a binder in stock feeds.

Example 5

In this Example, the formulations were trialed on three types ofmolluscs, the slug Deroceras reticulatum and the snails, Cochlicellabarbara and Helix aspersa. The trial was conducted within a temperaturerange of 12-17° C. for Deroceras reticulatum, 9-18° C. for Cochlicellabarbara and 12-17° C. for Helix aspersa. The dead snails were removedand counted after 8 days. The results are shown in Table 5.

TABLE 5 Comparison of the efficacies of various formulations containingdifferent amounts of clay in combination with FeEDTA. DerocerasCochlicella Helix Formulation reticulatum % barbara % aspersa %Formulation 14/15  93% 26/30 86% 8/15 53% 17 Formulation 14/15  93%26/30 86% 8/15 53% 18 Formulation 14/15  93% 22/30 73% 9/15 60% 19Formulation 15/15 100% 9/15 60% 20 Formulation 8/24 33% 21

Summary

It can be seen from the above results that slugs are considerably easierto kill than snails. It has been found that, generally, snails require ahigher concentration of active ingredient and a greater sophisticationin the design of the formulation used for efficacious results. From theabove, it can also be seen that the addition of a clay containingavailable Fe(III) ions can allow for a reduction in the amount of metalcomplexone required to obtain the same degree of efficacy.

In Examples 6 to 9, various formulations containing FeEDTA with andwithout FePO₄ and MgCO₃ were compared. All bait formulations were basedon a flour:bran weight ratio of 2:1.

The various formulations used were as follows:

Formulation 22 2.3% FeEDTA Formulation 23 2.6% FeEDTA + 5.7% CaCO₃Formulation 24 2.2% FeEDTA + 20.1% CaCO₃ Formulation 25 2.6% FeEDTA +4.36% MgCO₃ Formulation 26 2.3% FeEDTA + 0.88% FePO₄ + 0.62% MgCO₃Formulation 27 2.3% FeEDTA + 1.21% FePO₄ + 1.13% MgCO₃ Formulation 282.3% FeEDTA + 1.86% FePO₄ + 0.93% MgCO₃ Formulation 29 2.5% FeEDTA +2.40% FePO₄ + 1.32% MgCO₃ Formulation 30 2.4% FeEDTA + 2.19% FePO₄ +2.69% MgCO₃ Formulation 31 2.6% FeEDTA + 3.50% FePO₄ + 3.00% CaCO₃

Example 6

In this Example, the following formulations were trialed on Helixaspersa. The feed was carrot. The trial was conducted within atemperature range of 12-17° C. for Helix aspersa. The dead snails wereremoved and counted after 9 days. The results are shown in Table 6. ThepH of each of the formulations was determined and is also presented inTable 6.

TABLE 6 Comparison of the efficacies of various formulations containingFeEDTA with and without additional iron phosphate and magnesium orcalcium carbonate. Formulation #1 #2 #3 #4 #5 #6 Total pH Formulation 221/2 0/2 0/2 1/2 0/2 0/2 2/12 6.2 Formulation 23 1/6 3/6 4/6 4/6 12/24*7.3 Formulation 24 2/2 2/2 1/2 1/2 2/2 1/2 9/12 7.4 Formulation 25 2/62/6 1/6 2/6  7/24* 8.3 *number of dead snails after 10 days, plot sizesapproximately three times standard i.e. 1.5 L and total internal surfacearea 900 cm³.

Summary

Comparison of Formulation 22 with Formulations 23, 24 and 25 illustratesthat the addition of calcium or magnesium carbonate enhances the killrate. It is believed that this enhancement is due both to a change in pHand the ease with which the iron is replaced by either the calcium ormagnesium ions in the active ingredient. The results from these examplessuggest that calcium ions are more effective at enhancing the kill ratethan magnesium ions.

Example 7

In this Example, the following formulations were trialed on Helixaspersa. The feed was carrot. The trial was conducted within atemperature range of 12-17° C. for Helix asperse. The dead snails wereremoved and counted after 7 days. The results are shown in Table 7.

TABLE 7 Comparison of the efficacies of various formulations containingFeEDTA with and without additional iron phosphate and calcium ormagnesium carbonate. Formulation #1 #2 #3 #4 #5 #6 Total Formulation 221/2 0/2 0/2 1/2 0/2 0/2 2/12 Formulation 26 1/2 0/2 1/2 1/2 1/2 1/2 5/12Formulation 27 2/6 4/6 3/6 2/6 11/24* Formulation 28 1/2 0/2 1/2 1/2 1/21/2 5/12 Formulation 29 5/6 2/6 3/6 3/6 13/24* Formulation 30 3/6 2/61/6 3/6  9/24* Formulation 31 2/6 4/6 3/6 2/6 11/24* *number of snailsdead after 10 days, plot sizes approximately three times standard i.e.1.5 L and total internal surface area 900 cm³.

Summary

Comparison between Formulation 22 and Formulations 26 to 31 illustratesthat the addition of iron orthophosphate together with magnesiumcarbonate enhances the kill rate.

Example 8

In this Example, the following formulations were trialed on Helixaspersa:

Formulation 32 5.17% CuEDTA + 5.73% CaCO₃ Formulation 33 5.17% CuEDTA +5.73% CaCO₃ + 0.24% SDS

The feed was carrot. The trial was conducted within a temperature rangeof 12-17° C. for Helix aspersa. The dead snails were removed and countedafter 6 days. The results are shown in Table 8.

TABLE 8 Comparison of the efficacies of various formulations containingCuEDTA and CaCO₃ with and without surfactant. Formulation #1 #2 #3 #4Total Formulation 32 2/6 1/6 1/6 0/6  4/24 Formulation 33 1/6 4/6 3/62/6 10/24

Summary

Comparison of Formulation 32 with Formulation 33 illustrates that theaddition of surfactant more than doubles the kill rate.

Example 9

In this Example, the following formulations containing ferrichydroxyethylethylenediaminetriacetic acid were trialed on Helix aspersa:

Formulation 34 3.36% FeHEEDTA Formulation 35 2.99% FeHEEDTA + 11.1%CaCO₃

The feed was carrot. The trial was conducted within a temperature rangeof 12-17° C. for Helix aspersa. The dead snails were removed and countedafter 6 days. The results are shown in Table 9.

TABLE 9 Comparison of the efficacies of various formulations containingFeHEEDTA and CaCO₃. Formulation #1 #2 #3 #4 Total Formulation 34 1/6 2/63/6 1/6  7/24 Formulation 35 2/6 5/6 3/6 2/6 12/24

Summary

Comparison of Formulation 34 with Formulation 35 illustrates that theaddition of calcium carbonate significantly enhances the kill rate.

Example 10

In this Example, the following formulations were trialed on Helixaspersa.

Formulation 36 2.0% FeEDTA + 1.9% FePO₄ + 0.18% SDS + 3.6% CaCO₃Formulation 37 2.6% FeEDTA + 3.50% FePO₄ + 3.00% CaCO₃ Formulation 382.3% FeEDTA

The daily temperature range was 1 8-28° C. and the dead snails wereremoved and counted after 4 days. The results are shown in Table 10.

TABLE 10 Comparison of the efficacies of various combinations of FeEDTA,with or without a surfactant, an additional source of Fe(III) ions orCaCO₃. Formulation #1 #2 #3 #4 #5 #6 Total Formulation 36 1/3 1/3 2/32/3 3/3 1/3 10/18 Formulation 37 1/3 2/3 0/3 1/3 2/3 0/3  6/18Formulation 38 1/3 0/3 2/3 0/3 0/3 1/3  4/18

Summary

Comparison of Formulation 36 with Formulation 37 illustrates that theaddition of surfactant markedly enhances the kill rate. Comparison ofFormulations 36 and 37 with Formulation 38 illustrates that the presenceof additives, including a surfactant and an additional source of ferricions, together with calcium carbonate, which raises the pH of theformulation, significantly enhance the kill rate.

Overall Summary

The results illustrate the variability in the kill rate obtained by theaddition of surfactant, by an additional source of Fe(III), such asferric orthophosphate and by a metal carbonate to the metal complexonein the bait composition. It is believed that the mechanism of action ofthe surfactants is that they increase the rate of the absorption of theFe(III) ions allowing them to pass rapidly through the intestinalepithelium and so into the blood stream of the mollusc leading to itsdeath. It is believed that the enhancement in efficacy obtained on theaddition of ferric orthophosphate is that the latter complexes with thephytates present in the flour, thereby allowing the Fe(III) ions of theFeEDTA to take part in the molluscicidal activity, whilst the partplayed by the metal carbonate is that of a pH adjustment agent, whichmakes the bait more palatable and therefore increases the amount ofpoison ingested. The presence of calcium ions is also believed to aid inthe release of ferric ions from the metal complexone to enable them totake part in molluscicidal activity.

The effect of all of these additives on the molluscicidal efficacy ofthe bait composition, containing a metal complexone as the activeingredient, has been clearly shown. The results illustrate that thereare optimal amounts of the respective additive and the complexone thatmust be reached to achieve the highest kill rates. The variation in theamount of bran used proportionally to the amount of Fe(III) ions usedand the effect this variable has on the efficacy of the bait has alsobeen illustrated. In general, the higher the concentration of availableFe(III) ions in the bait formulation, the higher the resulting killrate. In addition, the more palatable the bait, the higher thelikelihood of the bait being ingested and therefore the greater theefficacy of the bait as a stomach-action molluscicide. In addition, thepresent invention has also illustrated the way in which the variousadditives can be used to reduce the amount of FeEDTA required to achieveoptimum kill rates, thereby reducing the cost of producing an effectiveenvironmentally-acceptable stomach-action molluscicide.

Those skilled in the art will appreciate that the invention describedherein is susceptible to variations and modifications other than thosespecifically described. It is to be understood that the inventionincludes all such variations and modifications. The invention alsoincludes all of the steps, features, compositions and compounds referredto or indicated in this specification (unless specifically excluded)individually or collectively, and any and all combinations of any two ormore of said steps or features.

What is claimed is:
 1. A stomach-action molluscicide including aneffective amount of a metal complexone of ethylenediaminetetra-aceticadd (EDTA) or hydroxyethylethylenediaminetriacetic acid (HEEDTA), aneffective amount of at least one additive, excluding a metal carbonate,for enhancing the molluscicidal activity of the metal complexone,wherein said additive is a surfactant, an additional source of ferricions, or a combination thereof, and a non-liquid carrier for the metalcomplexone and additive components of the molluscicide, wherein themetal complexone is [Fe(III)(OH)EDTA]²⁻, the dimer [EDTA-Fe—OFe-EDTA]⁴⁻,or FeHEEDTA, and wherein the amount of metal complexone is between about1-7% of the weight of the molluscicide.
 2. A stomach-action molluscicideaccording to claim 1, wherein the additive is a surfactant.
 3. Astomach-action molluscicide according to claim 2, wherein the surfactantis selected from the group consisting of cationic, anionic and non-ionicsurfactants.
 4. A stomach-action molluscicide according to claim 3,wherein the anionic surfactant comprises sodium dodecyl sulphate (SDS),calcium benzyl dodecyl sulphate (ALKANATE CS®), or ammonium dodecylsulphate (ADS).
 5. A stomach-action molluscicide according to claim 4wherein the surfactant is sodium dodecyl sulphate (SDS).
 6. Astomach-action molluscicide according to claim 3, wherein the non-ionicsurfactant is sorbitan monostearate or sorbitan monooleate.
 7. Astomach-action molluscicide according to claim 2, wherein the amount ofsurfactant is between about 0.05-1% of the weight of the molluscicide.8. A stomach-action molluscicide according to claim 1, wherein theadditive is an additional source of ferric ions.
 9. A stomach-actionmolluscicide according to claim 8, wherein the source of ferric ions isselected from a ferric salt or a clay.
 10. A stomach-action molluscicideaccording to claim 9, wherein the ferric salt is ferric orthophosphate.11. A stomach-action molluscicide according to claim 10, wherein theamount of ferric orthophosphate is between about 1-5% of the weight ofthe molluscicide.
 12. A stomach-action molluscicide according to claim1, wherein the additive is a surfactant in combination with anadditional source of ferric ions.
 13. A stomach-action molluscicideaccording to claim 12, wherein the additional source of ferric ions isferric orthophosphate.
 14. A stomach-action molluscicide according toclaim 1, wherein the non-liquid carrier for the metal complexoneincludes a mollusc food, a mollusc phagostimulant, a water-proofingagent, a flavouring agent, a preservative, a filler, a lubricant and aneffective amount of a pH adjustment agent.
 15. A stomach-actionmolluscicide according to claim 14, wherein the pH adjustment agent isCaCO₃, K₂CO₃, or MgCO₃, or a combination of these, or CaSO₄.
 16. Astomach-action molluscicide according to claim 14, wherein the amount ofthe pH adjustment agent is between about 1-5% of the weight of themolluscicide.
 17. A stomach-action molluscicide according to claim 16,wherein the pH of the molluscicide is non-acidic when added to water.18. A stomach-action molluscicide according to claim 17, wherein the pHis between about 7 and 10 when added to water.
 19. A stomach-actionmolluscicide according to claim 18, wherein the pH is about 8 when addedto water.
 20. A stomach-action molluscicide according to claim 1,wherein the amount of metal complexone is between about 2-3% of theweight of the molluscicide.
 21. A stomach-action molluscicide accordingto claim 1, wherein the metal complexone comprises a metal complexone incombination with at least one other molluscicide.